Magnetothermal Properties of Heat Transport in Cobalt Chloride Thiourea

Thermal-conductivity measurements have been made on a single crystal of cobalt chloride thiourea, Co${\mathrm{Cl}}_2$·${\left[\right(\mathrm{N}{\mathrm{H}}_2\left)\mathrm{C}\mathrm{S}\right]}_4$, in the temperature range 0.35-20 K and in applied magnetic fields of up to 20 kG. Below the Néel temperature of 0.92 K, an enhancement in conductivity for heat flowing in the [001] sublattice-magnetization direction is interpreted as due to the onset of spin-wave conductivity. Data taken for heat flowing in a normal [110] direction show no such enhancement. Relatively sharp changes in the conductivity as a function of temperature and magnetic field have been used to obtain information on the paramagnetic-antiferromagnetic and antiferromagnetic—spin-flop phase boundaries. Magneto-thermal-resistance resonances in the paramagnetic state have yielded information on the magnitude and anisotropy of the $g$ value for the unpaired electronic state of the cobalt ion.